I'm out of touch with RF technology lately. But there are some immediate applications that I can think of, where a community approach can yield interesting resu

I'm out of touch with RF technology lately. But there are some immediate applications that I can think of, where a community approach can yield interesting results. That 'long wavelength' part in your question would necessitate receiver antennas with a large radio aperture to get some reasonable spatial resolutions - sometimes on the order of kilometers. The practical way in which this problem is addressed is using signal processing techniques like Aperture Synthesis and Very Long Baseline Interferometry (VLBI). If the worldwide community can share the cost by deploying cheap receivers and donating compute time, it can lead to some interesting results. Much of these already exist, but they do have room for innovations and improvements. It's also a fun way to demystify these seemingly esoteric concepts.